Fluid pressure producing device



a .F. LOWEKE 2,303,289

FLUID PRESSURE PRODUCING DEVICE Filed July 29, 1940 INVENTOR.

Patented Nov. 24,1942 2 4 N ED STATES, PATE astazss FLUID PRESSUREraon'ucme limes I Erwin F. Loweke, Hydraulic Brake Detroit, Mich,assignor to Company,

Detroit, Mich, a

corporation of California Application July 29,1940, Serial No. 348,298

5 Claims. v(c1. (id-54.6)

This invention relates to fluid pressure braking systems, and moreparticularly to fluid sure producing devices for'such systems.

Broadly the invention comprehends a fluid An object of the invention isto provid e a fluid pressure system including a fluid pressure producingdevice having means inhibiting accumu--' lation of air and gasbubblesin-thesystem.

Another object of the fluid pressure braking system including a fluidpressure producing device comprisingmeans for maintaining apredetermined pressure on :the fluid in the system and so controllingthe flow of develop therein.

Other objects and advantages of the-invention will appear from thefollowing description taken in connection with the accompanying drawing,in which invention is to provide a t fluid as to dispel anyair or gasbubbles thatmay Fig. 1 is a schematic view of a fluid pressure brakingsystem embodyingithe invention;

Fig. 2 is a vertical sectional view of a fluid pressure producing deviceincorporated inthe system; and

Fig. 3 is a sectional view substantially on line 3-3, Fig. 2. j

Referring to the drawing for more specific details of the invention, Itrepresents generallya fluid pressure producing device including areservoir l2, having a filling opening 14, normally closed as by a plugl6 provided with openings l8 forventing the reservoir to the atmosphere.

A cylinder 20 at the base of the reservoir includes a small chamber 22and a relatively large chamber 24 arranged'forward of the small chamber,concentrically thereto, and in direct communication. therewith, andproviding at its juncture'with the small chamber an annular shoulder26.

The small chamber 22 is open at its outer end,"

and arranged in the wall thereof are spaced ports 28 and 30 providingcommunications between the reservoir and the small chamber, and thelarge chamber 24 is closed at its, outer-end by a head 32 provided witha discharge port 34 controlled as by a two-way valve indicated generallyat 36.

As shown, the head 32 body portion 18 has a concentrically'55 pistonhead '52 slidable in the disposed chamber 38 communicating with thechamber 24 and the discharge port 34. A shell in the chamber has a head42 40 suitably secured provided with a concentric opening 44 and a valveseat 46 on its back surrounding the opening. A. valve 48 for is normallyurged The valve 48 includes a cylindrical bodyportlon has a section 54ofreduced diameter extended through and movable in the opening in thehead of the shell, and extended axially from the section 54 is a valvestem 56 concentrically'disposed with relation to the chamber 24,'thepurpose of which will hereinafter appear. At the juncture of the bodyportion-52 and the reduced section there is provided a shoulder 58having a profile correspondingto that of the valve seat 46 forcooperation therewith; i

The body of the valve 48 hasa concentrically disposed chamber 60communicating with a passage 62 extended through the stem 56. A plug 64closes one e'nd of the chamber 60, and a passage 65 through the plugiscontrolled by a ball valve 68 urged toits' seat'by a spring.

A piston 10 re'ciprocable in the cylinder 20 is I held againstdisplacement by a washer" seated on an annular shoulder in the open endof'the' chamber 22 and' secu rin 14 seated in a groove inthe wallet thecylinder.

The piston '10 includes a head 16, a reduced, 7 providing in conjunctionwith the-wall or the chamber 221m annular chamber communicating with thereservoir l2 as by way of the port 28, an'da skirt 82 supporting asealing cup 84 forinhibiting seepage of fluid from the cylinder past thepiston, and arranged in the back of the piston is-a socket 86.

The head 16 of the piston has a plurality of spaced passagestherethrough providing com. munication's' betweeny theannular chamber 80and thatportion of the chamber 22 forward of the head 16 of-the piston,and a sealing cup positioned on the head li'controls thepassages 88. Aconcentric extension 92 on the piston head '16 supports a pistonhead 94reciprocable in the chamber 24. The head 84 and the extension 92 areconcentrically bored to provide a passage 96 communicating withthechamber 22 by way of a restricted port 91. This passage receives thestem 56 of the valve and communicates with the passage 2 therethrough,and" the has a plurality of spaced passages oFncE cooperation with theseat 48 v to closed position by a spring 50 interposed between the valveand the head 32;"

shell 40.- This body portion red in place by a retaining I ll. sleevedon the valve stem thepisto ,stem I, and a the chamber 22 for the lltherethrough providing communications beto its retracted position.

A fluid pressure delivery pipe or conduit lil4 branches connectedactuated motors I", preferably pairs, one pair for actuating, brakesassociated with the front wheels of a vehicle, and another pair foractuating brakes associated with the rear wheels of the vehicle.

As shown.

plate backing plate, a pair of iriction elements 2 pivoted on thebacking. plate for cooperation with the drum.

a retractile spring I I4 connecting against displacement and also toa,sos,asa

the brakes are of conventional type 1 becomes ei'iective the shoes, anda motor corresponding to-the motors I" mounted on the backing plate andconnected to the of the shoes into engagement with the drum against theresistance of the retractile spring.

A thrust pin H has one end seated in the socket It in the back of thepiston II, and on the other end of the thrust pin is.-a coupling Illconnected by a flexible boot l2l to the open end of shoes and operativefor activation exclusion of dust from thecylinder. The coupling illreceives one end of a rod I22, and the other end of the rod is pivotallyconnected to a foot pedal lever I24 rockable on a stub shaft I26 andconnected as by a retractile spring I22 to a fixed support. 1

In a normal operation, upon foot pedal lever I24, iorce-is transmittedtherefrom through the rodl22 and thrust pin lit, to the piston 1|,resulting in movement of the piston on its compression stroke. Duringthe initial movement or t piston on its I stroke, the cup ll closes theport 82. and fluid in the chamber 24 forwardof the piston head 24 isdisplacedthereirom, pastthe valve 42, through the discharge port 34 andfluidpressure delivery line or conduit I04 thereof into the fluidpressure actuated motors I05, causing energization of the motors-withthe resultant activation of the friction elements or shoes H2 intoengagement'with the drum llii against the resistance of. the retractilesprings H4 to effectively retard rotation of the drums.

During initial actuation of the piston, a large volume of fluid israpidly displaced from the large chamber 24 past the valve 42 andthroughthe discharge port I4 and lines I24 into the motors i0. quicklymoving the brake shoes ment with the drums ill, and, thereafter, uponfurther movement of the piston on its compression stroke, the pressureon the fluid in the system 1 forward of the piston rapidly increases.when the pressure on the fluid reaches a predefluid pressure deliveryThis results in compression and the f respective branches.

I I2 into engagedepressing the I I termined degree, the valve S2 cracks,and fluid v is gradually metered past the valve 88 through the valvechamber 60, the passage 62 in th valve stem into the passage 92, thencethrough the restricted port 91. into the chamber 22, until the pressureson the fluid in the chambers 22 and 24 become equalized. Immediatelyupon equalizing the pressure on the fluid fore and aft of the pistonhead t4, the pistonhead It becomes eflective 30 completely flllingthechambers.v

, ceiving a quantity of fluid in ing a double diamet'ral chamber and alarge chamber, a discharg port Upon completion of a braking operation,the s appliedor operative force on the foot pedal lever is released, andthe lever returns to its retracted position under the influence of theretractile spring I28. This results in retracting the rod Ill and thrustpin H6 and the consequent release or the piston 10, whereupon the springit! to move the piston to its retracted position.

As the pistonmoves to its retracted position, a partial vacuum .iscreated in the chamber 24. This resultsin drawing fluid from thereservoir l2 through theport 22 intotheannular chamber 20, thencethrough the passages II in the piston head It, pastthe cup ll, into thatportion of the chamber 22 forward of the piston head", thence throughthe passages II in the piston head 04, past the sealing cup ,lOlLintothechamber 24,

During this operation. fluid is returning to the cylinder from themotors I02, and the fluid pressure deliverylines connecting the motorsto the cylinder, under the influence or pressure on the fluid in themotors andfluid pressure delivery lines, introduced by the ,retractilesprings H4. The pressure'onthe fluid so returning to the cylinder cracksthe valve 68, past the valve 68 through the chamber 80, the passage 82in the valvestem, the Passage I in th piston and the restricted port llinto the chamber 22. This results in the chamber 22 reexcess or itscapacity, and this excess of fluid is displaced from the cylinder 22through 'the port 20 into the reservoir. It will be apparentthat thevalve 26 not only precludes air and gas bubbles from the cylinder, butalso operates to compensate for expansion and contraction of thefluid inthe system, due to temperature changes and also maintains a positivepressure on the fluidin the system.

sons skilled in the art. The invention is, thereas indicated by thescope fore, to be limited only of the appended claims.

Having the invention, secure by Letters Patent is,-'-

1.,A fluid pressure producing device compriscylinder having a small forone of the, chambers, a valve for control of the discharge port fluidfrom the valve through at least one of the chambers, a pistonreciprocable in the cylinder having heads commensurate with therespective chambers and a passage therethrough providing communicationbetween the means and the small chamber.

2. A fluid pressure producing device comprising a double diametralcylinder having a small chamber, a large chamber forward of the smalland the fluid then flows thus described thevarlous features of what Iclaim as new'and desire to having means for conveying valve for controlof the discharge port having a chamber and a discharge port for thelarge chamber, a two-way valve for control of the discharge port havinga hollow stem for delivery of fluid from the valve through the largechamher, a piston reciprocable in the cylinder having spaced headscommensurate withthe respective chambers and a passage therethroughconnecting the hollow stem with the small chamber.

3. A fluid pressure producing device comprising a double diametralcylinder having'a small chamber, a relatively large chamber forward ofthe small chamber and in communication therewith and a discharge portfor the large chamber, a two-way valve for control of the discharge porthaving a hollow stem for delivery of fluid from the valve through thelarge chamber, and a piston reciprocable in the cylinder having spacedheads commensurate with the respective chambers and a passagetherethrough providing communication between the hollow stem and thesmall chamber.

4. A fluid pressure producing device comprising a double diametralcylinder having a small chamber, a relatively large chamber arrangedforward of, concentric thereto, and in direct communication with thesmall chamber, and a discharge port for the large chamber, a two-wayhollow stem for delivery of fluid from the valve through the largechamber, and a piston reciprocable in the cylinder having spaced headscommensurate with the respective chambers and a concentric passagetelescoping the stem of the valve and communicating with the smallchamber. 5. A fluid pressure system comprising a reservoir, a doublediametral cylinder supplied there- 'from having a small chamber, a largechamber arranged forward of the small, anda discharge port for the largechamber, fluid pressure delivery means connected to the discharge port,fluid pressure actuated means connected to the delivery means, a two-wayvalve for the discharge port operative to maintain a positive pressureon the fluid in the fluid pressure actuated means, means carried by thevalve for delivery of fluid from the valve through the large chamber, apiston reciprocable in the chamber having spaced heads commensurate withthe respective chambers and a passage therethrough, communicating withthe means carried by the valve and with the small chamber. I

ERWIN F. LOWEKE.

